Abstract: To face the increasing demand for long lasting, versatile and performing machines, a
detailed analysis of the load conditions is required especially when structural integrity assessment
has to be achieved. Usually acquisitions of load histories are shorter than the machine working life
and an extrapolation of the signal for the total service life is needed. Traditional methods for load
spectra extrapolation are based on conservative choices in terms of worst case scenario. Methods
based on extreme value statistics have been developed.
The problem addressed in this paper concerns the extrapolation of load histories on a welded
boom in which different manoeuvres are superimposed. Different ways of extrapolating the load
measurement have been derived, both in time domain and in Markov domain, in order to account
for the superposition of bigger and more damaging cycles and smaller cycles caused by two
different service operations.

Abstract: Normal mode force appropriation is a method of physically exciting and measuring
the undamped natural frequencies and normal mode shapes of a structure. Traditionally used
in the aerospace industry for ground vibration testing, it is capable of accurate normal mode
estimates. The method attempts to determine multi-point force vectors that will induce single
mode behaviour, thus allowing each mode to be viewed in isolation. However it fails to tackle
changing dynamic response with forcing level of excitation in nonlinear systems. The method
of Force Appropriation for Nonlinear Systems or FANS, produces a special appropriated force
vector resulting in nonlinear response. The structure responds dominantly in the target linear
mode shape permitting the direct nonlinear characteristics of that mode to be identified in the
absence of cross coupling effects.

Abstract: This paper examines the dynamics of a single degree of freedom nonlinear model,
representing a quarter of an automobile with a semi-active, nonlinear suspension. Assuming that
the kinematic excitation caused by the road surface profile is harmonic, the principal resonance
and frequency entrainment are obtained for regions of the model parameters. Changing the
excitation frequency and road profile amplitude we analyze possible chaotic vibrations and
bifurcations of the system.

Abstract: In real mechanical situations it is a certainty there will be non-linear behaviour
present at a range of frequencies and amplitudes. It is not, however, always possible to have a
priori knowledge of the input to a system. A method has been developed by Adams to allow
the experimental engineer to overcome such problems. The technique is addressed in this paper
and applied to both simulated and experimental data. The method makes use of time domain
characterisation via work and characteristic diagrams and also the frequency domain approach
toward non-linear identification from feedback of the outputs, (NIFO). This paper attempts to
use these time and frequency domain techniques to locate, characterise and quantify non-linear
behaviour using both simulated and experimental data.
The approach to this work is to obtain simulated data from a quarter car model and real
data taken from an experimental rig. The data will be taken at a variety of frequencies and
amplitudes and the above time and frequency domain techniques will be applied.

Abstract: This paper presents a two-stage meta-heuristic approach to producing weight-optimised
solutions needed prior to the detailed finite element analysis of composite wing. Composite wing
covers are assumed to take the form of a group of stiffened sub-panels with varying skin and
stiffener geometries according to the wing layout and loads. A population of limited solutions
satisfying various design constraints was created using layout (skin and stiffener geometry),
selected lay-ups, rule based stacking sequence and various assumed loads. The closed form
analytical solutions of flat stiffened orthotropic plates are used for calculating buckling reserve
factors and strength margins. For each sub-panel, a meta-heuristic rule was imposed to search for a
suitable combination of skin and stiffener geometry. The criterion used was minimum weight
satisfying laminate continuity accounting for manufacturability. Later, the optimised solutions for
each sub-panel are converted into a format supported by the conventional finite element tool
(NASTRAN). The use of meta-heuristic approach and their automation in Visual Basic for
Applications resulted in fast convergence and potential time-saving compared to genetic algorithms.

Abstract: Recent NATO funded research on methods for detection and interpretation
methodologies for damage detection in aircraft panel structures has motivated work on low-order
nonlinear analytical modelling of vibrations in cracked isotropic plates, typically in the form of
aluminium aircraft panels. The work applies fundamental aspects of fracture mechanics to define an
elliptical crack, and the local stress field and loading conditions, arbitrarily located at some point in
the plate, and then derives an analytical expression for this that can be incorporated into the PDE for
an edge loaded plate with various possible boundary conditions. The plate PDE is converted into a
nonlinear Duffing-type ODE in the time domain by means of a Galerkin procedure and then an
arbitrarily small perturbation parameter is introduced into the equation in order to apply an
appropriate solution method, in this case the method of multiple scales. This is used to solve the
equation for the vibration in the cracked plate for the chosen boundary conditions, which, in turn,
leads to an approximate analytical solution. The solution is discussed in terms of the perturbation
approximations that have been applied and highlights the phenomenology inherent within the
problem via the specific structures of the analytical solution.

Abstract: When carrying out a vibration modal analysis of a structure it is usually assumed that the
structure is in vacuo. However as structures become increasingly light and thin walled due to the
development of high grade corrosion resistant alloys, this fundamental assumption is becoming
increasingly strained. In this paper we will highlight the analysis and the implications of
structural/fluid interaction on modal analysis for the purpose of prediction of dynamic response and
for vibration health monitoring.

Abstract: This article presents apparently the first application of Meshless local Petrov-Galerkin
(MLPG) method for 3-D elasticity analysis of moderately thick rectangular laminated plates. As
with other Meshless methods, the problem domain is represented by a set of spread nodes in all
three dimensions of the plate without configuration of elements. The Moving Least-Squares (MLS)
method is applied to construct the required shape functions. A local asymmetric weak formulation
of the problem is developed and MLPG is applied to solve the governing equations. Direct
interpolation method is employed to enforce essential boundary conditions. Details of formulation,
numerical procedure, convergence and accuracy characteristics of the method are investigated.
Results are compared, where possible, with other analytical and numerical methods and show good
agreement.

Abstract: Ultrasonically assisted turning (UAT) is a novel material-processing technology, where
high frequency vibration (frequency f ≈ 20kHz, amplitude a ≈15μm) is superimposed on the
movement of the cutting tool. Advantages of UAT have been demonstrated for a broad spectrum of
applications. Compared to conventional turning (CT), this technique allows significant
improvements in processing intractable materials, such as high-strength aerospace alloys,
composites and ceramics. Superimposed ultrasonic vibration yields a noticeable decrease in cutting
forces, as well as a superior surface finish. A vibro-impact interaction between the tool and
workpiece in UAT in the process of continuous chip formation leads to a dynamically changing
stress distribution in the process zone as compared to the quasistatic one in CT. The paper presents
a three-dimensional, fully thermomechanically coupled computational model of UAT incorporating
a non-linear elasto-plastic material model with strain-rate sensitivity and contact interaction with
friction at the chip–tool interface. 3D stress distributions in the cutting region are analysed for a
representative cycle of ultrasonic vibration. The dependence of various process parameters, such as
shear stresses and cutting forces on vibration frequency and amplitude is also studied.